Hiapo is Niuean barkcloth — paper mulberry beaten thin, aged to a smoky tan, then drawn on freehand with dark plant ink. Samoan and Tongan tapa is rubbed over a carved board, so it repeats. Niuean hiapo is painted by hand, so it does not.
The 1880s fine-line sheets did two things no other Polynesian barkcloth did: they carried human figures, and they carried names. This system keeps that logic — one ink, one ground, a drawn line that varies in weight, and no empty margin anywhere.